Mandrels are employed for bridging between generally cylindrical supporting structural surfaces and objects typically surrounding such structural surfaces for establishing engagement between the generally cylindrical structural surface and the object. For example, mandrels are used to bridge between a driving shaft and roll-like spools of paper being wound or unwound from a cylindrical tube generally surrounding the shaft. Where an inflatable mandrel is employed in bridging, the inflatable mandrel may be also employed to exert a pressure upon the surrounding object such as a cylindrical tube forming a part of a roll-like spool and may thereby lift the cylindrical tube centeringly about the generally cylindrical supporting structure and may be employed also to impart rotational motion from the cylindrical supporting shaft to the spool-like cylindrical tube.
Inflatable mandrels also can provide outwardly directed pressure against a surrounding object, and where the surrounding object is malleable or flexible, can cause the surrounding object to conform to contours of a second object surrounding the first.
Inflatable mandrels typically are formed by laying up fabric plies on a drum or cylinder to form one or more pairs of membranes that define an inflation chamber between individual membranes of the pairs. Typically the membranes are formed of laid-up fabric plies, both surfaces of each of the fabric plies having a rubberized coating applied thereover. The laid-up fabric plies are then vulcanized to form coherent, clearly defined membranes. Typically the cylinder drum on which the inflatable mandrels is built are of a collapsible nature, that is such drums can be distended for forming an inflatable mandrel and then collapsed slightly to facilitate removal of the formed inflatable mandrel therefrom.
Such collapsible building drums are generally expensive to purchase, and where it is desired that a mandrel of a substantial length, such as in excess of about ten feet, be built, purchase costs for collapsible building drums can become prohibitive, particularly where required for speciality inflatable mandrels where only a few units of a particular diameter are to be built. Where a mandrel building drum is not collapsible, removal of a long, finished mandrel from such a non-collapsible building drum can become a complicated, difficult matter. Typically, such formed inflatable mandrels are stretchable to a certain degree because of the rubbery characteristic necessary for desirable inflation properties, and pulling upon a formed mandrel to effect sliding removal from a building drum can cause a chinese handcuff effect functioning to seat the mandrel more firmly upon the building drum at a point where the mandrel stretches slightly during efforts to effect removal. Likewise, placing a completed mandrel upon a cylindrical supporting structural surface can be complicated by the same chinese handcuff effect.
A mandrel relatively easily removable from a building drum upon completion without necessitating the collapse of the building drum and relatively easily placed upon a generally cylindrical structural supporting surface for mandrel operations could find substantial utility in a variety of industries ranging from winding spools to pipe lining operations. Likewise, a method for forming such a readily removable/installable inflatable mandrel could find application in enhancing the mandrel manufacturing process.